The disclosure generally relates to aromatic bisphenols prepared using a catalyst system. More particularly, the disclosure relates to aromatic bisphenols prepared using heteropolyacid catalysts, clays and functionalized metal oxide catalysts.
Bisphenols are valuable raw materials for producing polycarbonates. Polycarbonates are widely used in a variety of applications by virtue of their excellent physical properties, such as impact resistance, mechanical characteristics, transparency, and the like. Bisphenols are generally obtained by the reaction of a carbonyl compound with a phenol in the presence of an acidic catalyst, such as mineral acids or acidic ion exchange resins. One example of such acidic ion exchange resins is a sulfonated polystyrene resin cross-linked with divinylbenzene in the hydrogen form, (PS-DVB). Frequently, a co-catalyst is used in conjunction with the acidic catalyst, to improve the selectivity for bisphenol such as the para, para-bisphenol isomer, for example. Co-catalysts may be present as unattached molecules in the bulk reaction matrix, i.e., “bulk co-catalysts”, or may be attached to the acidic resin catalyst through ionic or covalent linkages. Mercaptans are one class of co-catalysts that may be employed. More specifically, thiols, e.g., organosulfur compounds derived from hydrogen sulfide, are used as co-catalysts. Numerous efforts have been made to improve the selectivity for bisphenols by varying the mercaptan co-catalyst and the acidic catalyst. One approach that has been attempted is to use a catalyst having an attached co-catalyst, which is prepared, for example, by reacting a portion of the acidic groups of the acidic ion exchange resins with amino-mercaptans, to provide catalysts containing both mercaptan and sulfonic acid groups.
When ion exchange resin catalysts are used for making bisphenols by reaction of phenols with carbonyl compounds, the lifetime of the catalyst is affected by numerous factors, such as, for example, mechanical strength and fouling tendency. In addition, ion exchange resin catalysts typically require a pre-conditioning step, especially in continuous processes. Pre-conditioning is generally performed by passing the phenol through a packed bed of the ion exchange resin catalyst.
There remains a need in the art for alternative catalysts for preparing bisphenols that have superior mechanical properties, compressibility, non-swelling nature and hydrothermal stability as compared to the traditionally used ion-exchange resin catalysts, thereby leading to improved catalyst lifetime and/or productivity and bisphenol productivity.